1. Field of the Invention
This invention relates to a gear shift mechanism for a gear mounted on a shaft within a housing of a power transmitting device and, more specifically, to such a gear shift mechanism which can be selectively locked in one of two positions.
2. Description of the Prior Art
It is not uncommon for power transmitting devices to include gear shift mechanism which have locking features to prevent accidental and undesired engagement or disengagement of mating gears in the transmitting device. As evidenced by U.S. Pat. Nos. 2,434,051; 2,577,019; 2,969,690; 3,015,986; 3,405,596; 3,534,921 and 3,772,941, many different and some complicated shift mechanisms have been utilized to prevent the undesired shifting of the gears during the operation of such a power transmitting device.
While these above mentioned devices might work quite satisfactorily to prevent undesired movement of the gear, some are quite complicated and expensive to provide. Therefore, it is not uncommon in power transmitting devices to utilize a well known type of shift rod which is mounted parallel to the shaft including the gear to be shifted, which shift rod is capable of being moved axially to produce corresponding axial movement of the gear on the shaft. To prevent undesired axial movement of this type of shift rod, the housing for the power transmitting devices includes a ball and spring detent system having a ball member which is biased into a detent in the exterior surface of the shift rod. While these devices have also been successfully utilized in the past, there are some instances when power transmitting devices of this type generate sufficient force on the gear to overcome the resistance created by the ball-detent device of the shift rod and cause it to be relocated from the desired position. It is, therefore, a continuing problem to insure that such a gear shift mechanism will include a sufficiently reliable locking system to prevent undesired gear movement during any unusual or transitory operating conditions.